Description:
------------
A regression was introduced in php 5.3.9 to the file ext/openssl/openssl.c which causes openssl_encrypt("", "aes-128-cbc", "password") to use uninitialized memory when calling the underlying AES_cbc_encrypt() whenever the length of the $data argument is zero.  This results in either a corrupted return value, or a segmentation fault, depending upon what exists in php's memory heap.

I bisected the code difference between php 5.3.8 and 5.3.9 and have attached the errant patch to this bug report.

The problem patch introduces the following code, which for reasons unknown fails to call the update function whenever the length of the data argument is zero:
-       EVP_EncryptUpdate(&cipher_ctx, outbuf, &i, ...);
+       if (data_len > 0) {
+               EVP_EncryptUpdate(&cipher_ctx, outbuf, &i, ...);
+       }

Reverting the attached patch fixes the problem for me.

I'm seeing this problem on both x86_64 (64 bit) and i686 (32 bit) processor architectures.  OS is Slackware in both cases, with php linked against openssl version 1.0.0g (ditto for openssl 1.0.0e and 1.0.0f), glibc 2.14.1 and compiled with gcc 4.5.3.

The corruption/segfault occurs whether or not an initialization vector is passed to the function; the only requirement it seems is the zero-length data (ergo, the omission of the call to EVP_EncryptUpdate()).

Test script:
---------------
<?php
var_dump(openssl_encrypt("", "aes-128-cbc", "password",
                         false, str_repeat(chr(0), 16)));
$vec = str_repeat(chr(0), 16);
var_dump(openssl_encrypt("", "aes-128-cbc", "password",
                         false, $vec));
var_dump(openssl_encrypt("", "aes-128-cbc", "password"));

unset($vec);
$memory = "Let's use some memory!";
$vec = str_repeat(chr(0), 16);
var_dump(openssl_encrypt("", "aes-128-cbc", "password",
                         false, $vec));
?>

Expected result:
----------------
string(24) "xrQjTh0HCclFET5PKpYH9w=="
string(24) "xrQjTh0HCclFET5PKpYH9w=="

Warning: openssl_encrypt(): Using an empty Initialization Vector (iv) is potentially insecure and not recommended in test.php on line 7
string(24) "xrQjTh0HCclFET5PKpYH9w=="
string(24) "xrQjTh0HCclFET5PKpYH9w=="

Actual result:
--------------
GNU gdb (GDB) 7.2
Reading symbols from /usr/bin/php...done.
(gdb) set args test.php
(gdb) run
Starting program: /usr/bin/php test.php
[Thread debugging using libthread_db enabled]
string(24) "AMa0I04dBwnJRRE+TyqWB/c="
string(24) "xrQjTh0HCclFET5PKpYH9w=="

Warning: openssl_encrypt(): Using an empty Initialization Vector (iv) is potentially insecure and not recommended in test.php on line 7
string(24) "xrQjTh0HCclFET5PKpYH9w=="

Program received signal SIGSEGV, Segmentation fault.
0xb767cb7c in AES_cbc_encrypt () from /lib/libcrypto.so.1
(gdb)